Mechanical jack



Aug. 11, 1931. RE. MANLEY ET AL MECHANICAL JACK Fil ed Dec. 3, 1928 3Sheets-Sheet 1 11, R. E. MANLEY ET AL 1,818,077

MECHANICAL JACK I Filed D60. 5, 1928 5 Sheets-Sheet 2 abhor "e14 A g- 19 R. E. MANLEY ET AL 1,818,077

MECHANICAL JACK Filed Dec. 3, 1928 3 Sheets-Sheet 3 Patented Aug. 11,1931 UNITED STATES PATENT OFFICE 7 ROBERT E. MANLEY AND FREDERICK T.FLINCHBAUGH, OF YORK, PENNSYLVANIA,

.ASSIGNORS TO THE MANLEY MANUFACTURING COMPANY, OF YORK, PENNSYL- VANIA,A CORPORATION DELAWARE MECHANICAL JACK Application filed December 3,1928.

This invention relates to roller jacks for vehicles and moreparticularly to improvements in jacks primarily for use in garages forelevating axles of automobiles and for 6 moving such automobiles bymeans thereof with either their front or rear axle elevated.

The main object of the invention is to provide a light but strong ackwith operating devices which will facilitate the operation thereof. a

The jack includes a truck comprising a wheeled rectangular frameconstructed of standard bar members and special castings to which thebars are secured and so arranged as to provide a novel braced jackframe'which is low, relatively light, and of rigid construction forcarrying the jack lifting members as compared with the usual cast frameconstructions.

The lifting member is raised and lowered by means of a long screw whichis rotated so as to move a nut connected with the lifting member andaccording to this invention a two-speed operating means is provided toeffect a rapid movement of the lifting member to a position for liftinga load or away therefrom and a slow movement with a high leverage of thelifting member under load either for raising or lowering the load. Thepresent embodiment of the operating means includes an actuating andtowing lever pivotally connected with the jack frame having a cross baror handle which may be connected with the screw for rotating it rapidly,or the handle may be connected so as to permit the lever to beoscillated to actuate the operating means with a step by step movementfor raising or.lowering the lifting member when a load is restingthereon which could not be elevated by the turning movement of the crossbar. The cross bar on the lever provides operating means for actuatingthe lifting member and for towing the jack either with or without a loadas well as for spotting, that is, moving the jack so that its liftingmeans are properly positioned under the load to be raised.

In order to effect a quick spotting of the lifting member under the loadthe rollers on the front end of the jack frame are castor Serial No.323,440.

wheels and the frame is provided with an adjustable slide adapted to beprojected into the path of a pin carried by the lever; by swinging thehandle and lever downwardly the pin carried by the lever engages theprojected slide and further movement raises the rear end of the jackframe so that the jack can be quickly swung on its castors for spottingthe lifting member under the load without havingto reciprocate the jackback and forth until the desired position is obtained. The adjustableslide is preferably stepped to provide for different elevations of thelever for convenience of the operator and is provided with pedal meansfor projecting it outward and spring means for re tracting it when theslide is relieved of the weight of the lever.

The accompanying drawings show a practical embodiment of the inventionin which Figure l is a plan view of a jack for vehicles in accordancewith this invention;

Figure 2 is a side elevation thereof; and

Figure 3 is an enlarged detailed section thru the bearing showing inelevation the end portion of the screw.

Figure 4 is an enlarged side elevation partly in section of the loadlifting means.

Figure 5 is an enlarged detail section of the actuating and towing levermechanism.

Figure 6 is an end view of the handle.

Figure 7 is a transverse section thru the collar which surrounds thedrive shaft.

Figure 8 is a detailed plan view of the spotter used for facilitatingthe positioning of the jack under a member to be lifted.

Figure 9 is a side elevation of the same.

Figure 10 is a transverse section of the jack positioning lever.

Referring to the drawings the truck or main frame 10 of the jackcomprises a transverse front end casting 11 the ends of which aresuitably secured by means of machine bolts 12 to the front ends of sidebars 13 which extend lengthwise to the rear end of the frame where apair of castings 14 are secured to them. Castings 14: are each formedwith a socket 15 for receiving a transverse axle 16 and each is providedwith a set screw 17 for locking the castings in proper position withrespect to each other and the axle. The outer ends of axle 16 providebearings upon which rollers 18 are journaled, the outer surfaces ofcastings 14 being formed to provide side thrust bearings 19 for theinner sides of the rollers, and similar side thrust bearings 20 aremounted on the axle for the outer sides of the rollers and arepreferably secured in place by means of cotter pins 21 passing throughbifurcations 22 in the outer portions of the bearings and apertures inthe axle. In an intermediate position along the bars 13 are upwardly extendin castings 23 secured to the bars 13 by means of rivets 24, a studbolt 25 extending transversely of the frame, and by a pipe spacer 26positioned between the two bars 15. Upper load supporting side bars 27and 28 V are connected with the upper portions of castings 23, front endcasting 11 and rear end castings 14, respectively, extendinglongitudinally over the side bars 13. An outwardly extending bracketcasting 29 is secured. by means of rivets 30 to each of the bars 27 atpositions substantially equal to the length of the bars 28 away from thecastings and a downward projection 30a of each casting 29 is alsosecured by a rivet to the correspond ing underlying bar 13 so as tomaintain the bracket in proper position with respect to the bars of theframe. T he outward lateral pro jections 31 of the bracket castings 29provide bearings for castor wheels 32 which are ro tatably mounted inbifurcated supporting members 33 having bearings 3-4 engaging the underside of the projections 31 and vertical axles 35 projecting upwardlytherethrough. lVashers 36 are positioned on the upper and lower sides ofprojections 31 and cotter pins 37 are placed in apertures in the upperends of axles for securing the castor wheels to the frame.

It will be noted that the frame or truck consists of a number ofrelatively small castings,11, 14, 23 and 29,formed with the necessaryreinforcing webs and securing lugs for connecting them with the framebars 13., 27 and 28 which are relatively light steel members of standardconstruction whereby a light reenforced frame is provided as comparedwith a. frame entirely of cast parts which would not only beconsiderably heavier but more expensive to construct. It will also benoted that by this construction that a greater portion'of the load to becarried upon the upper portion of the intermediate castings 23 will betransmitted to thesupporting rollers 18 and 32 through the upper bars 27and 28 and as hereinafter set forth the castor rollers or wheels 32adjacent to the front end of the frame provide means for quicklybringing the frame to a required position as well as affording means forturning the frame as it is drawn along on its The load lifting meanscomprises a pair of levers 38 each having a hub 39 mounted on a shaft39a extending transversely of the frame 10 and journaled in bearings 40aformed in the upper portions of castings 23 with the hubs 39 each beingpositioned adj acent to the inner sides of the castings 23. Each lever38 consists of a down arm 40 for connection with operating mechanism anda lifting arm 41, cast integrally with their hub 39 in the form of abell crank, the outer extremities of the arms 40 and 41 being formedwith bearings 42 and 43 respectively for transverse axles 44 and 45.Axles 44 and 45 provide connections between the operating nut 46, fromwhich axle members 44 extend, and the down arms 40 of the levers 38 andbetween the lifting arms 41 of levers 38 and the lifting head 47 whichis supportedrrbyraxle members 45. The two levers 38 have their liftingarms 41 connected by means of a tie plate 48 secured to them by means ofbolts 49 so that the levers 38 are properly spaced and united as anintegral lifting lever.

The lifting head 47 includes a load engaging cap 50 and a downwardlyextending body portion 51 from which the axle members 45 extend, andthrough projections 52 at the lower rear extremity of the body portion51 is a pivot rod 53.- The normal upright position of the lifting head47 is maintained by means of drag links 54 connected with the pivot rod53 and a fixed pivot rod 55 so arranged that the drag links will have aparallel motion with respect to the lifting arms 41. Drag links aresecured on the pivot rods 53 and by means of cotter pins 56.

The operating means includes a long central screw 57, the threaded. endportion 58 of which cooperatively engages the operating nut 46 forholding the lifting head at any de sired elevation from the lowest tothe highest positions as indicated at A and B respectively in Figure 2of the drawings. The other end portion 59 of screw 57 extends through anapertured boss or bearing 60 of casting 11 and at its outer end isprovided with a beveled gear 61 secured in place by means of a Portion59 of the screw is of a re-.

pin 61a. duced diameter forming a shoulder at 590. against which athrust bearing 62 is seated; this may be a ball thrust bearing. Aspacing washer 63 engages the other side of the thrust bearing andbeyond that a sleeve member 64 is positioned 011 the screw. The outerend of sleeve 64 is spherically shaped to engage a complementary shapedportion on the casting 11 forming a bearing for this portion of thesleeve 64 whereby the sleeve may be rocked slightly with respect to thebearing as the screw isrotated and its threaded end is swung up or downin following the swinging position of nut 46 which is carried by thedown arm 40 of the lifting lever. The pori A ah A M .M ..1 1H... tiuiiof the aperture tiiruugu [1055' 608111- rounding the intermediateportion of sleeve 64 is of sufficient size to permit the slight rockingmovement of the sleeve and the boss is provided with a lubricator at 65to feed lubricant into the aperture to prevent wear between'the sleeveand its bearing and the end portion 59 of the screw turning within thesleeve.

In order to brace the frame 10 to counteract the effect of the load apair of tension rods 66 are connected between casting 11 and shaft 40 inthe upper portion of castings 23 upon which the lifting lever isjournaled. These rods pass through apertured bosses 67 formed on theupper side of casting 11 and are provided with nuts 68 which engage thebosses. The opposite ends of rods 66 are provided with nuts 69 whichengage a lateral flange 70 of a plate 71 extending from a hub 72 mountedon shaft 3960 between the two lever members 38. To apply a tension alongthe rods 66 the nuts 68 and 69 may be tightened; plate 71 is aperturedat 7 3 so as to permit free access for manipulating nuts 69 during theassembly of adjustment of the equipment.

Plate 71 is preferably formed with end flanges 74 extending from thelateral flange 70 and these flanges 74 are secured to bars 27 whichassure proper alinement and also afford additionalbracing for the frameand maintaining the lateral spacing of the upper portion thereof. Thehub 72 of this plate is preferably'apertured and shaft 39a iscorrespondingly apertured for receiving a cotter pin75 which preventsthe shaft from moving endwise or from'turning. Plate 71 has a lug 76extending downwardly from hub 72, the lower end 77 of lug 76 being.

enlarged and apertured for receiving the pivot rod 55, heretoforereferred to, and carrying it in a fixed position wlth respect to thelifting lever arms.

An actuating and towing lever with its handle generally designated as 78 is secured to front casting 11 of the frame by means of lug plates 79fastened to the casting between it and the bars 13 and 27 by means ofthe securing bolts 12 previously referred to. The outer ends of lugplates 79 are provided with bearings 80 in which a lateral shaft 81 isjournaled for pivotally connect ing a casting 82 of the lever to theframe 10.-

Casting 82 has a forwardly extending socket portion 83 and rearwardlyextending arms 84 provided with bearings 85 through which shaft 81passes to provide the pivotal connection' between the lever and frame.The socket 83 is slotted at 86 and is provided :with aperturedprojections 87 through which a bolt 88 passes to provide clamping meansfor holding the end of a. tubular extending member 89 of the lever inplace therein.

Mounted'between the arms 84 of casting 82:

pawl 92in a manner hereinafter set forth and in front thereof is asecond gear 93 of the gear train which is also rotatably mounted ,onshaft 81 and drivingly connected with gear by means of a tongue and slotconnection 94 between the hubs 95 and 96 of these gears. The casting 82is provided with a socket 97 in which a stub shaft is received andretained by means of a set screw 98; on this shaft is mounted the thirdgear of the train, a combined, spur gear 99 which meshes with spur gear93 and a beveled gear 100. Extending through the tube 89 and socket 83is a drive shaft 101 which is journaled adjacent to its lower end in abearing 102 formed through casting 82 beyond the socket 83. and on itsend is secured by means of a pin 103 the fourth or driving gear of thetrain, beveled gear 104 which meshes with beveled gear 100. It is to benoted that the rotation of the drive shaft 101 will eflect a rapidrotation ofthe screw 57 by means of the gear train and consequently 'afast movement of the operating nut 46 for quickly raising orlowering thelifting head 47 to any required position.

A cross bar 105 constituting a handle for the lever is mounted on thefront or outer end of the tube'89 and is actuatable for operating thejack and for towing it. This cross bar or handle comprises a sleeve 106which is flanged at each end as indicated at 107 and 108 and isrotatably mounted on the end of tube 89 with its flange 107 engaging .acollar 109 brazed to tube 89 as a'limiting abutment therefor. A flangedcollar 110 secured to the drive shaft 101 by means of a pin 111 forms anabutment-cooperating with the flange 108 at the other end of the sleeveto maintainit in proper position on the end of the tube. Sleeve 106 isprovided with laterally extending sockets 112 and 118 into which tubes114 and 115 of the cross bar are respectively secured. In the outer endof tube 114 is a sperically ended retaining plug 116 which is secured inplace by means of a pin or rivet 116a and in the outer end of the tube115 is a plug 117 similarly fastenedby a pin 117a. On this plug 117 is aknob 118 rotatably mounted on a screw 119 which secures the knob to theplug as a means for rotating the cross bar or handle v105 for turningthe drive shaft 101 inthe manner to be explained as follows:

I The sleeve 106 of the cross bar 105 has a longitudinal key-way 120extending through its socket112 and end flanges 107 and 108 in 106 butis adapted to be extended beyond either end of the sleeve; extendingoutward-- ly through the flange 107 it engages in notch 122 in thecollar 109 which prevents the cross bar from turning and holds it in ahorizontal position with respect to tube 89; extending outwardly in theother direction itis adapted to engage in any one of a plurality ofsimilar notches 123 in the flange of collar 110 (more clearly shown inthe detail Figure 5) so that the cross bar will turn with respect totube89 and by rotation thereof the drive shaft 101 will be turned. In theintermediate position,the key 121 does not project beyond either end ofthe sleeve, and the cross bar or handle is free to rotate to anyposition desired so that it may readily be brought to a position to belocked with either the drive shaft 101 or the tube 89. The key 121 isprovided with a finger piece 124 for manipulating it and a projection125 on sleeve 106' limits its movement in one direction while aprojection 126 from socket 112 limits it movement in the otherdirection. The key has three notches 127, corresponding to its three"positions, and a detent 128: on a sliding block 129 in tube 114 isyiel'dingly' held in engagement with any chosen one of the notches 127by means of a spring 130 in tube 114 behind block 120' between thisblock. and plug 116 as a retainer therefor;

The. lifting head 47 may be rapidly raised or lowered tov any desiredposition by turning the drive shaft 101 by rotating itwith the handle105 in the manner above set forth,

but when it is raising or lowering a load and av greater leverage isrequired than is ob'- tained in turning the handle the handle isreleased from the drive shaft 101 and locked to the tube 89 and then bybringing the pawl 92' into cooperation with the ratchet wheel 91 thelifting head with the load may be raised or lowered slowly with a stepby step movement by oscillating the actuating lever by means of thehandle up and down aroundits pivotal connection with frame 10. It is tobe noted that during'the latter operation of the handle and actuatinglever the drive shaft 101 is left free to rotate in the tube 89 andwith. respect to the handle or cross bar 105.

Pawl 92' has a comparatively wide tooth 131 for engaging the teeth ofratchet wheel 91 and may be turned to effect either an up rotation ofthe wheel or a down rotation thereof according to the direction in whichthe tooth of the pawl faces. In order that the pawl may be turned inthis manner it is formed? on the end of a cylindrical body portion 132which is rotatably and reciprocably mounted in a socket 133' extendinginwardly in the casting 82- anddirected toward the ratchet wheeland aspring 134 behind it isoperated to urge the pawl into engagement withthe ratchet wheel. The body 132 has a reduced cylindrical extension 135which passes through a corresponding aperture through casting 82extending concentrically from socket 133. The outer end of the extension135 is provided with a concentric aperture 136 for receiving the end 137of a central rod- 138 and is provided with lateral slots 139 throughwhich a pin 140 carried by the rod end 137 projects. This pin and slotconnection with the rod 138 provides means whereby the pawl may beturned for operating the ratchet wheel 91 in one direction or the otherfor retracting the pawl from the ratchet wheel altogether. Vhen the pawlis arranged to engage the ratchet wheel slots 139 permit longitudinalmovement of the pawl with respect to the control rod 138 as the pawl isforced backward against the spring 134 but when the control rod is drawnout far enough it will hold the pawl in a retracted position.

Mounted at an intermediate position on tube 89 is a clamp 141 comprisinga collar slotted at 142 and provided with apertured lugs 143 throughwhich a bolt 144 passes for fastening the collar in place on the tube.This clamp is provided with a downwardly extending member 145 ending ina foot 146 forming a support to keep the actuating lever 78 fromstriking the ground. The clamp is also provided with a side projection147 which is apertured at 148 for receiving the control. rod 138; theprojection, as shown in F'gures 1 and 7, is cup shaped and provided withdeep upper and lower slots 149' and 150 and a shallow side slot 151 forreceiving a laterally bent end 1520f the controlrod 138. It will benoted that when the end 152 of the control rod is positioned in theupper slot 149 pawl 92 is positioned to engage ratchet wheel 91 in sucha: manner as to effect an elevation of the lifting head 47 by theswinging movement of the lever 7 8. lVhen the control rod is turned withthe end 152 positioned in the lower slot 150 pawl 92' is turned toelfecta lowering of the lifting head by the swinging operation of thelever and handle and when the end 152 of the rod is positioned in theside slot 151 the pawl is turned sidewise and retracted from the ratchetwheel altogether and in this position the rapid movement ofthe liftinghead by rotating the drive shaft 101 with the handle or cross bar 105 isbest effected. V

In order to facilitate the positioning of the jack under a member to belifted the jack is provided with a spotter. This includes a trip lever153 pivotally supported at its fulcrum on an end 154 of shaft 81, thelaterally extending arm 155 of the lever being pr0- vid'ed with a pedal156 and the upwardly extending arm 157 having an operating pin 158 forprojecting a slide 159 outwardly, as best shown in Figures 8 and 9.Slid'e'1'59 restson the upper portion of bearing 80' and extends througha rear guide 160 secured to frame 10 by means of the bolts 12. The guideis provided with a lateral extension 161 which carries a pin 162 uponwhich a spring 163 is mounted so as to engage a lateral eXten sion 16%on the slide so as to normally hold the slide in its retracted position.Pin 162 functions as a stop against which the extension 16lengages as a.limit to the forward movement of the slide and its rearwardmovement islimited by a downward projection 165 on its front end which engages withthe front of bearing 80. The forward end of slide 159 also has an upwardprojection 166 which is provided with a vertical slot 167 in which theoperating pin 158 of the lever engages for projecting the slideoutwardly and the end of the slide is form-ed with two steps 168 and 169having an intermediate inclined portion 170 between them. These steps ofthe slide are adapted to be positioned so as to be engaged by alaterally projecting pm 171 on the casting 82 when the lever 7 8 isswung downwardly, but they are normally ield in the retracted positionby spring 163.

In the operation of the ack, when it is desired to position the liftinghead 47 under a member to be raised the jack is rolled adjacent to themember and then the head may be quickly spotted thereunder by depressingpedal 156 so as to project either the lower or upper step, 168 or 169,in the path of pin 171.

Lever 78 is then swung down, pin 171 engages the step and by furtherdownward movement of the lever the rear end of the jack frame 10 iselevated so that the jack rests onthe two front castor wheels 32 and theof key 121 and rotating the cross bar. The keyis now moved so as to lockthe cross bar in a horizontal position; the end 152 ofithe control rodis positioned in the upper slot 1.49 so that pawl 92 will engage ratchetwheel 91 so as to effect an upward movement of the lifting head and thehandle is then raised and lowered, swinging the lever about the shaft.81 and thus raising thelifting head withv a step by step movement untilthe required elevation is attained. The lowering of the lifting head isefiect-ed by a similar lever operationof the lever by first positioningthe end 1520f the control rod in the lower slot 150; afterwards, whenthe head has been relieved of its load the control rod may be positionedwith its end 152 in slot 151,

a neutral or out position, and the cross bar 105 connected againbyfmeans of key 121 with drive shaft 101 and the cross bar or handleturned to. lower quickly the liftingher with a step by step movement byan oscil lating movement of the lever, and rotatable means caried byfthelever operable to turn the rotatable member to facilitate a rapidmovement of the lifting member.

2. In a lifting jack, the combination with.

a frame, a lifting member pivotally mounted on the frame, and arotatable'member connected with the lifting member for elevating andlowering it, of an actuating lever pivotally connected with the frame,and a pawl carried by the lever for operating the rotatable member witha step by step movement of the lever, said pawl being rotatably mountedand adapted to be positioned to drive said rotatable member in eitherdirectionto effecteitheran elevating or a lowering of the liftingmember.

3. Ina lifting jack, the combination with a frame, a lifting memberpivotally mounted on the frame, and a rotatable member con nected withthe lifting member for elevating and lowering it, of an actuating leverpivotally connected with the frame, a pawl carried by the lever foroperating the rotatable member with a step by step movement of thelever, said pawl being rotatably mounted and adapted to be positioned todrive said rotatable member'in either direction toeffect eitheran'elevating or a lowering of the lifting member, means for retractingsaid pawl to an inoperative position, and rotatable means carried by thelever operable to turn the rotatable member to facilitate a rapidmovement of the lifting member.

4:. In a lifting jack, the combination w1th a frame and, a liftingmember mounted on the frame, of a two speed operating means including alever operable to effect a slow actuation ofthelifting member and meanscarried by the lever operable to effect a rapid ciated with the lever.for actuating the rotatable means for the lifting'member with a Step bystepmovement, and means for conlar necting the rotatable means with thehandle 'tobe turned thereby to efiect a rapid raising or lowering of thelifting member- 6. In a lifting jack, the combination with a frame, alifting member mounted thereon, and rotatable means for raising andlowering the lifting member, of an operating lever pivotally connectedwith the frame, a handle adapted to rotate on the lever and securedthereto for towing the jack, a drive shaft carried by the lever, andconnections between the handle, drive shaft and rotatable means wherebythe lifting member may be guickly raised or lowered by turning the hande.

7 In the combination set forth in claim 6 in which the connectionbetween the drive shaft and rotatable means is a train of gears whichpermits the swinging of the lever with respect to the frame ofthe jack.

8. In the combination set forth in claim 6 in which the connectionbetween the drive shaft and rotatable means is a train of gears whichpermits the swinging of the lever with respect to the frame of the jack,a ratchet wheel on one of the gears of the gear train, and a pawlcarried by the lever adapted to engage said ratchet wheel and effect astep by step rotation of said rotatable means by swinging movement ofthe lever.

9. In the combination set forth in claim 6 in which the connectionbetween the drive shaft and rotatable means is a train of gears whichpermits the swinging of the lever with respect to the frame of the jack,a ratchet wheel on one of the gears of the gear train, and a pawlcarried by the lever adapted to engage said ratchet wheel and effect astep by step rotation of said rotatable means by swinging movement ofthe lever, and means for disconnecting the drive connection between thehandle and said drive shaft and for connecting the handle in ahorizontal position on the lever to facilitate the lever operation ofthe lifting member.

10. In a lifting jack, the combination with a truck frame, front andrear rollers supporting the frame, a lifting member mounted on theframe, and an actuating lever pivotally connected with the front of theframe, of means for limiting the swinging movement of the lever withrespect to the frame whereby the lever may be operated to effect anelevating of the rear end of the frame to free the rear rollers and tosupport the jack entirely on the front rollers to facilitate spottingthe lifting member under a load to be elevated thereby.

11. In a lifting jack according to claim 10, means for securing thelever at different angles with respect to the frame whereby the rear endof the frame may be raised with the lever at different elevations.

12. The combination according to claim 10 in which the means forsecuring the lever with respect to the frame includes a projection onthe lover, a slide carried by the frame, a pedal for positioning theslide in the path of said pro ect1on, and means for normally retractingthe slide to permit free swinging 14. In a lifting jack, the combinationwith'.v

a frame, a lifting member pivotally mounted .on the frame, and arotatable member connected with the lifting member for elevating andlowering it, of an actuating lever pivotally connected with the frame,and a pawl carried by the lever for operating the rotatable member witha step by step movement of the lever, said pawl being rotatably mountedand adapted to be positioned to drive said rotatable member in eitherdirection to ef-- fect either an elevating or a lowering of the liftingmember, a drive shaft carried by the lever, a handle adapted to beconnected with said drive shaft for turning it, and atrain of gearsconnecting said drive shaft with said rotatable member.

15. In a ack including a lifting member, a roller truck consisting offront and rear end members, side bars interconnecting the end members,intermediate load members extending upwardly from said side bars forsupporting the jack lifting member, load supporting bars interconnectingthe upper portion of said intermediate members and each of the endmembers, and front and rear wheels for supporting the load transmittedthereto through said lifting member, intermediate members and loadsupporting bars.

16. In a lifting jack, as set forth in claim 15, a pivotal supportcarried by the upper portion of said intermediate members, a liftingmember on said pivotal support comprising a bell crank lever having anoutwardly extending lifting arm and a downwardly extending operatingarm, a lifting head supported by the lifting arm, an operating nutcarried by the down arm, a long screw having one end threaded throughsaid nut and its other end rotatably supported by the front end memberof the truck, and means for turning said screw for raising and loweringthe lifting member.

17. In a lifting jack as set forth in claim 15, a pivotal supportcarried by the upper portion of said intermediate members, a liftingmember on said pivotal support comprising a bell crank lever having anoutwardly extending lifting arm and a downwardly extending operatingarm, a lifting head pivotally supported by the lifting arm so as to tiltwith respect to the lever as the lever is swung on its support, and draglink bars mounted at the under side of said lever and pivotallyconnected with the lifting head for maintaining it in an erect positionwith respect to the lever at all times.

18. In a lifting jack as set forth in claim 15, a pivotal supportcarried by the upper portion of said intermediate members, a liftingmember on said pivotal support comprising a bell crank lever having anoutwardly extending lifting arm and a downwardly extending operatingarm, a lifting head supported by the lifting arm, an operating nutcarried by the down arm, a long screw having one end threaded throughsaid nut and its other end rotatably supported by the front end memberof the truck, means for turning said screw for raising and lowering thelifting member, and tensioning means interconnecting the front endmembers of the truck and the pivotal support for the lifting lever tocounteract the thrust through the screw between the lever and the endmember, including a pair of tensioning rods connected at their lowerends with said front end member, a hub on said pivotal support, a plateextending from said hub with which plate the upper ends of said rods areconnected, a downwardly extending lug on said hub, a pivot carried bysaid lug, a pivot carried by the liftitng head, and drag linksconnecting said last two pivots to cause said lifting head to turn withrespect to its support on said lever for maintaining it in an erectposition with respect to said lever at all times.

19. In a jack including a lifting member, a roller truck consisting offront and rear end castings, side bars interconnecting the end castings,intermediate load supporting cast ings extending upwardly from said sidebars for supporting the lifting member, load supporting barsinterconnecting the upper portion of said intermediate castings, atransverse shaft carried by the rear end castings, supporting wheels onsaid shaft, lateral bracket castings connected with the load supportingbars adjacent to the front end of the truck, and supporting wheelsmounted under said brackets, whereby the load on the lifting member willbe transmitted through said load supporting bars to the supportingwheels.

20. In a jack the combination with a support, a lifting memberconsisting of a lever pivotally mounted on said support and having adownwardly extending arm, a nut carried by said arm, a screw having itsinner end extending through said nut, a bearing formed on the outer endof the screw carried by said support, means for turning the other end ofthe said screw in said bearing, said bearing including a socket having aspherically shaped recess through which said screw extends, and a sleeveon the screw having a

